Percussion bit

ABSTRACT

The invention concerns a bit of the percussion type having a bit body with slots for receiving hard blocks, such as cemented tungsten carbide blocks. The slots taper outwardly toward the bottom and the blocks also taper outwardly toward the bottom and are introduced endwise into the slots, preferably with an interference fit. Keys are provided for locking the blocks in the slot.

United States Patent [72] Inventor Jack Miller Bedford, Pa. [21] Appl.No. 762,236 [22] Filed Sept. 16, 1968 [45] Patented Feb. 16, 1971 [73]Assignee Kennametal Inc.

Latrobe, Pa.

[54] PERCUSSION BIT 7 Claims, 5 Drawing Figs.

[52] US. Cl 175/410, 175/420 [51] Int. Cl E21c13/01 [50] Field of Search175/398, 399, 409-414, 415-420 1 References Cited UNlTED STATES PATENTS993,972 5/1911 English 175/410X Brossoit Erickson Burt Williams..

Signell Alexander et a1 .1

Dahlin et al.

Kinzbach Primary Examiner- David H. Brown Attorney-MelvinA. Crosbyl75/41OX 175/410X 175/410X 175/410 175/41OX 1'75/41OX PATENTED FEB1 6I971 FIG-5 v INVENTOR. J RCK M LLE R PERCUSSION BIT The presentinvention is concernedwith a percussion bit having hard inserts mountedtherein in a novel manner and to a method of mounting the hard insertsin the percussion bit.

Percussion bits of the nature referred to generally take the form of ahigh strength steel body with hard inserts mounted in the working end ofthe body for engagement with the formation being drilled. The insertsare usually made of cemented tungsten carbide and are normally brazed inplace in the steel bodies. The brazing of the inserts in place in thesteelbodies, however, is not only time consuming and expensive but thedifferential expansion and contraction of the carbide material of theinserts and the body which can lead to premature failure of one or theother or both thereof.

The primary objective of the present invention is the provision of arock bit structure in which the hard carbide inserts are held in placein the steel body without brazing.

Another objective of this invention is the provision of the percussionbit and a method of making the same in which no high temperatures areemployed during the mounting of the inserts into the body so thatthermalstresses are not developed in the inserts and body. v i

The objectives referred to as well as other objectives and advantages ofthe present invention will become more apparent upon reference to thefollowing detailed specification taken in consideration with theaccompanying drawings, in which:

FIG. I is a perspective view showing a typical percussion bitconstructed according to the present invention;

FIG. 2 is a fragmentary perspective view showing in more detail thenovel manner of mounting the hard inserts into the body of the bit;

FIG. 3 is a vertical sectional view indicated by line Ill-III on FIG. 2;r

FIG. 4 is a fragmentary view showing another manner of securing aninsert in place in the bit body and;

FIG. Sis a sectional view indicated by line V-V on FIG. 4.

Referring to the drawings in more detail, in FIG. I, indicates a bitbody of substantially conventional shape. The bit body tapers from asmaller end 12 to a larger end 14. The larger end is the working end ofthe bit and the bit is adapted for being secured at its smaller end 1210a suitable actuating motor as by means ofa threaded bore in the bitbody.

The working end of the bit body is in the form of a plurality of boxlikewings 16, each of which has a-slot or pocket 18 therein extendingsubstantially radially of the bit body and open at its radially outerend andat the top, which is the side of the pocket toward the working ofthe bit end. Mounted in each slot I8 is a block 20 of hard wear.resistant material; cemented tungsten carbide, for example.

As will be seen in FIG. 2, each slot 18 has its sidewalls 22 and 24converging toward the open side of the slot. Similarly, each block 20has its sidewalls 26 and 28 converging toward the wedge-shaped tip 30 ofthe block which projects from the working end ofthe bit. The walls 26and 28 of block 20 at any transverse section there through are at leastslightly farther apart than the sidewalls 20 and 24 of the slot 18 atthe same level. Each block 20 thus has an interference fit in its slot18. The block 20 can be pressed into position in the slot, butpreferably, the bit body is heated to expand the slot 18 and then, whilethe body is hot, the unheated block 20 is put in place in the slot andwhich assembling operation might be accompanied by the application ofpressure.

The tapering configuration of the block in the slot in which it isdisposed prevents the block from coming out of the bit body in the axialdirection but the possibility exists that the block will shift in thedirection of the length of the slot under the heavy impacts to which itis subjected in use. In order to prevent the block from shifting axiallyin its slot, the block is preferably formed with a groove 32 extendingto an angle of the length of the block, and when the block is mounted inits slot, groove 32 registers with a groove 34 formed in the adjacentsidewall of the block. The registering grooves form a keyway forreceiving a key to lock the block in its slot.

When the block is in position in its slot and grooves 32 and 34 are inregistration to form the keyway, a key in the form of a pin 36 is drivenor pressed into the registering grooves. Pin 36, which may be round butis preferably somewhat oval, terminates near the bottom wall 38 of theslot and extends past a bore 40 formed in the bit body and intersectinggroove 34.

Pin 36 is fixedly held in place in grooves 32 and 34 as by welding orbrazing or the like in bore 40 as indicated 42 in FIG. 3. It will beapparent that pin 36, for ease of manufacture, extends in an axial planeof the bit body but it is not necessary for the pin to extend in exactlythis direction in order to prevent block 20 from shifting laterally inits slot.

FIGS. 4 and 5 show a modification in which the block 20a mounted in slot184 of bit body 10a is provided with a pair of recesses 44 in onesidewall. These recesses 44 register with holes 46 in the bit body whenthe block is in position in its slot. Steel pins 48 are inserted inholes, as by pressing, or bores 46 so that they extend into the recesses44 in block 20a and weld ing or brazing as at 50 is placed in the outerends of bores 46 to hold the pins 48 in place.

One, or the other, or both, of each notch and block, near the bottom ofthe notch and block, are relieved to avoid the creation of extremelyhigh localized stresses at the corners of the notch which could lead tocracking of the bit body. This is done, as shown in FIG. 2, by relievingthe inner corners of the block as at 52, which can be done by forming abevel on the inner corners of the block or by rounding the corner of theblock with a relatively large fillet. It would as also be possible torelieve the notch in the region of the bottom corner of the block if sodesired.

In the manner described above, the blocks are joined to the bit bodieswithout heating the bit body and, therefore, without setting up thermalstresses and strains in the carbide blocks and in the bit body whichcould lead to premature failure of the bit. Also, the cost and time thatgo with brazing the blocks in place in the bodies is eliminated so thatthe bit can be produced more economically than according to prior artpractices.

Modifications and adaptations of the present invention falling withinthe scope of the appended claims will occur to those skilled in the art.

Iclaim:

1. In combination; a steel body having a peripheral wall and slot meansin the form of at least one slot in the body and block means of hardcemented metal carbide in said slot means in the form of at least oneblock; said slot means being closed on the bottom and the sides and openat the top and at one end intersecting said peripheral wall so as tohave at least one open end accessible from the side of said body, saidslot having the same width from end to end between said sides in anygiven transverse plane, said sides of the slot converging toward theopen top of the slot, said block being insertable axially into said slotand substantially filling said slot with a portion of the blockprojecting beyond the open top of the slot, the sidewalls of said blockconverging toward said portion of the block at substantially the sameangle as the sides of said slot and engaging the said sides of the slotwhen the block is disposed in the slot, the bottom end of said blockopposite said portion thereof engaging the bottom of said slot, thesidewalls of said block being spaced farther apart in any giventransverse plane than the sides of the slot located in the same planeprior to mounting the block in the slot whereby the block has aninterference fit in the slot, and key means disposed between said blockand said body at one side of said block and engaging both said block andsaid body and locking the block to the body to prevent movement of theblock longitudinally of the slot.

2. The combination according to claim 1 in which at least one sidewallof said block has recess means extending laterally into a sidewallthereof near the bottom of the sidewall, said body having bore meansregistering with said recess means when said block is disposed in'saidslot, and said key means comprising steel plug means fixed in said boremeans and projecting therefrom into said recess means.

3. The combination according to claim 2 includes welding fixing saidplug means in said bore means.

4. The combination according to claim 1 in which said key means is inthe form of steel rod means disposed between at least one sidewall ofthe block and the adjacent side of the slot and at an angle to thelength of the slot, said one sidewall of the block and the adjacent sideof said slot having registering groove means therein closely receivingsaid rod means.

5. The combination according to claim 4 which includes connecting meansfixing said rod means to at least one of said block and said body.

1. In combination; a steel body having a peripheral wall and slot meansin the form of at least one slot in the body and block means of hardcemented metal carbide in said slot means in the form of at least oneblock; said slot means being closed on the bottom and the sides and openat the Top and at one end intersecting said peripheral wall so as tohave at least one open end accessible from the side of said body, saidslot having the same width from end to end between said sides in anygiven transverse plane, said sides of the slot converging toward theopen top of the slot, said block being insertable axially into said slotand substantially filling said slot with a portion of the blockprojecting beyond the open top of the slot, the sidewalls of said blockconverging toward said portion of the block at substantially the sameangle as the sides of said slot and engaging the said sides of the slotwhen the block is disposed in the slot, the bottom end of said blockopposite said portion thereof engaging the bottom of said slot, thesidewalls of said block being spaced farther apart in any giventransverse plane than the sides of the slot located in the same planeprior to mounting the block in the slot whereby the block has aninterference fit in the slot, and key means disposed between said blockand said body at one side of said block and engaging both said block andsaid body and locking the block to the body to prevent movement of theblock longitudinally of the slot.
 2. The combination according to claim1 in which at least one sidewall of said block has recess meansextending laterally into a sidewall thereof near the bottom of thesidewall, said body having bore means registering with said recess meanswhen said block is disposed in said slot, and said key means comprisingsteel plug means fixed in said bore means and projecting therefrom intosaid recess means.
 3. The combination according to claim 2 includeswelding fixing said plug means in said bore means.
 4. The combinationaccording to claim 1 in which said key means is in the form of steel rodmeans disposed between at least one sidewall of the block and theadjacent side of the slot and at an angle to the length of the slot,said one sidewall of the block and the adjacent side of said slot havingregistering groove means therein closely receiving said rod means. 5.The combination according to claim 4 which includes connecting meansfixing said rod means to at least one of said block and said body. 6.The combination according to claim 5 in which said body has a boreextending therein and intersecting the groove means in the body near thebottom of said slot and said connecting means connects said rod means tosaid body and is in the form of a fused connection of said rod means tosaid body where said bore intersects said groove means.
 7. Thecombination according to claim 6 in which said fused connection iswelding and said bore is substantially filled with welding.